function toggle(e) {
  console.log('callback ran');
  e.target.classList.toggle('danger');
}

document.querySelector('button').addEventListener('click', toggle);

const posts = [
  { title: "帖⼦⼀", body: "这是帖⼦⼀" },
  { title: "帖⼦⼆", body: "这是帖⼦⼆" }
 ];
 
function getPosts() {
  setTimeout(() => {
  posts.forEach((post) => {
  const div = document.createElement("div");
  div.innerHTML = `<h3>${post.title}</h3><p>${post.
 body}</p>`;
  document.querySelector("#posts").appendChild(div);
  });
  }, 1000);
 }
 getPosts();

 function createPost(post, cb) {
  setTimeout(() => {
  posts.push(post);
  cb();
  }, 2000);
 }
 createPost({ title: "帖⼦三", body: "这是帖⼦三" }, getPosts);
